The present invention relates to an intervertebral disc prosthesis, intended to be substituted for fibro-cartilaginous discs ensuring a bond between the vertebrae of the spinal column.
Various types of intervertebral disc prostheses are known in the prior art. Numerous prostheses, such as for example in the patent application FR 2 846 550 and WO 02 089 701, are constituted in a lower plate and an upper plate forming a sort of cage around a central core. A part of these prostheses enables the upper plate to swivel in relation to the central core and optionally permits the central core to slide in relation to the lower plate. This sliding of the central core in relation to the lower plate is an essential characteristic, as it must allow spontaneous positioning of the core in the ideal position to absorb constraints imposed on the prosthesis, during movements made by the patient wearing the prosthesis. The displacement of the core, co-operating with at least a plate about an uneven surface, enables an inclination between the plates of the prosthesis which facilitates the mobility of the patient wearing the prosthesis. The displacement of the core also prevents it from creeping when subjected to major constraints.
In this context, it is significant to propose a prosthesis which allows to impose a permanent inclination between the plates and induces, for example, lordosis. Depending on the disorder of the spinal column of the patient wearing the prosthesis, it is sometimes preferable that the prosthesis allows a correction of this disorder. In line with the wishes of the surgeon, the displacement of the core should be restricted in at least one direction. However, when the patient moves, the relative position of the elements of the prosthesis can be modified, within the permitted range of displacement.
One aim of some embodiments of the present invention is to propose an intervertebral disc prosthesis allowing limited movements of the different pieces of the prosthesis between one another and comprising a core used to restrict its displacement in at least one direction.